Interpretive Summary: Water conservation and improved water management are critical to sustaining arid irrigated agriculture. Pre-plant irrigation is an aspect of irrigation management that has not been well researched or discussed. When properly managed it has a significant role to play in improving irrigation water management during the growing season, and sustaining crop yield. pre-plant irrigation is the application of water during fallow periods to accomplish a goal in addition to plant growth and development, the traditional reasons for irrigation. These additional goals include germination of crops, weed control, soil water management, soil salinity management, fumigation, and fertilization. Use of pre-plant irrigation is practiced by both organic and chemical based agriculture. A single well timed and properly applied pre-plant irrigation can refill the soil water content in the soil profile, leach accumulated salt from the root zone, and provide water for crop germination. This ensures that the crop will get off to a good start and will be sustained through the growing season. Proper management includes considering the depth of water needed to refill the root zone, the leaching requirement needed to manage the salt, and providing uniform distribution of water. Pre-plant irrigation is an integral part of effective irrigation water management and will lead to improved water use efficiency and the extension of existing water supplies.

Technical Abstract:
Irrigation is the artificial application of water to support crop growth in both arid and humid areas. Pre-plant irrigation is the application of water in fallow periods to accomplish goals in addition to plant growth and development. Identified uses for pre-plant irrigation include germination, salinity management, fumigation, weed control, and fertilizer placement. The depth and timing of the application depend on the following: the irrigation goals, the water quality, the existing stored soil water, the soil salinity, the crop rotation, the crop salt tolerance, and the depth to shallow ground water. When used for germination water is applied and stored in the soil and the seed is planted into the stored water and germinates. After germination the soil cover is removed to aid the plant development. Soil salinity in the root zone is leached during the process of pre-plant irrigation for germination if extra water is applied above that needed to replenish soil water. A small pre-plant irrigation is used to germinate weed seeds that can be killed by either cultivation or chemical sprays. Refilling the soil water in the crop root zone is often necessary to minimize crop water stress during the growing season. Water stored deep in the soil profile is available late in the growing season when crop demand is the highest and oftentimes irrigation is inadequate to meet the demand.